The invention is directed to a process for the production of zeolites having the surface modified with organosilanes.
It is known to replace phosphates in washing agents (detergents) with crystalline zeolites of the type NaA4 which have a specific particle size distribution.
However, it has been found that zeolites with a small particle size have a tendency to agglomerate in the production of the washing agent. The agglomerate thus formed impairs the effectiveness and in the most unfavorable case deposits on the wash. One possibility of reducing the tendency of powdery materials to agglomerate is to modify the surface.
It is known to react water free zeolites with silanes at elevated temperatures. However, this is a matter of Y-zeolites which are present in the exchanged H-form. They were reacted at temperatures between 250.degree. and 650.degree. C. with tetramethylsilane and subsequently their activity as catalysts tested. (McAteer, J. J. Rooney "Proceedings of the 3rd Int. Conference on Molecular Sieves", J. B. Unterhaeven, Editor, Zurich, Sept. 3-7, 1973, pages 258-265).
Furthermore, it is known to treat zeolites in the Na-form with organosilanes (Hertzenberg U.S. Pat. No. 4,138,363, German OS No. 2,843,709 and Campbell U.S. Pat. No. 4,243,545) and in this manner reduce the tendency to agglomerate. Thereby the calcium binding capacity of the zeolite is only insignificantly influenced which is significant for inclusion in detergents.
However, a condition for the employment of the silane according to this process is that after the reaction of the alkoxy group with the zeolite the silane still has a further reactive group such as, e.g. acryl, epoxy, or amino groups.
Only the presence of these groups causes the above induced improvement in properties of the surface modified zeolites.
The production of this type of silane, however, is associated with great expense which makes the product correspondingly expensive.
The reactive groups of the silane still remaining after the reaction with the zeolite surface moreover results in the modified zeolites not being compatible with all surface active agents which customarily are used in detergents.
The object of the invention is to produce a zeolite having the surface modified with silanes which avoids these disadvantages.